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Monday, July 27, 2015

Astronomy Questions and Answers

Dale Alan Bryant

I'd like to thank Mike Petrasko for inviting me here to share some my experiences in astronomy, which, more often than not, included Mike himself! I'm an Amateur Astronomer with something like 35 years of experience being bent over the eyepiece of a telescope (and boy is my neck sore!) Mike and myself have had, probably some of the most interesting, sometimes bizarre (but usually entertaining) experiences in the history of observational astronomy. I will share them with you here as I recall them...

M66 Imaged by Adam Block

After having read my recent article on supernova SN1989B, my brother (not an astronomer!), texted me the following questions one night, included here with my answers:

Q: In your article, you talked about a star going supernova. If there was a planet with life orbiting the star, how much warning would their scientists have to save their civilization? A: Scientists would know about the star’s condition long before it went supernova and would have had time to prepare—that is, if there were actually any other place to go. However, after the explosion, the ejected material from the star would be traveling toward the planet at 10% of the speed of light and would reach the planet within just a few hours. The planet would be vaporized instantly. Q: So, what could happen to our Sun to cause us a problem here on Earth?

A: The Sun has done nothing out of the ordinary in its entire history. It is a very stable star. It has an 11-year sunspot and solar flare cycle which occasionally causes us electrical problems here on Earth, but that’s about it. Its internal nuclear forces are able to balance its gravitational forces which will not allow it to collapse in on itself and then explode.

Q: So the Sun will never go supernova?

A: No, the Sun is not massive enough. Only stars 3 solar masses and more can go supernova. A supernova explodes after it uses up its nuclear fuel and collapses under it own weight. What’s left, if it has enough mass, will collapse even further to the point of no return and become a black hole—with a gravitational pull so strong that not even light can escape. If the star doesn’t have enough mass to become a black hole, it may become a sphere of carbon under pressure. We all know what happens to carbon under extreme pressure—it becomes diamond! Yes, there are stars out there that are pure diamond. "Up above the world so high, like a diamond in the sky” was more accurate than anybody knew, at the time! But if it continues to collapse, it will become a neutron star; literally a ball of neutrons packed so tightly together that a teaspoonful would weigh millions of tons!

Q: So, just what will happen to the Sun?

A: The Sun, being a rather small star (specifically, a type G2 Yellow Dwarf), will begin to swell as it ages and move off the Main Sequence of stellar evolution to become a red giant star—a very slow process so no surprises here. Its edges will reach out to almost the orbit of the Earth. This is not good news for anybody sticking around as the Earth will be burned to a cinder! But there will be plenty of time to prepare; it will not happen for another 4.5 billion years.

Q: How are we related to all of this, supernovae I mean?

A: Well, the heavy elements such as iron, nickel, copper, magnesium, zinc, beryllium and the rest of the metals that make up terrestrial planets like Earth, and even our own bodies, were forged in the interiors of supernovae. That’s the only place in the universe these elements are created, along with minerals and silicates that become rock, sand and dust. They travel across space together to cool and condense into planets - and people! So, the atoms in our bodies once existed in the interiors of stars! To quote the late Cornell University professor of astronomy, Carl Sagan - “We are all star stuff.”